Powder paints, method for production and use thereof

ABSTRACT

Powder coating materials preparable by  
     (1) mixing at least two liquid components comprising in each case at least one liquid starting product in a static mixer, to give a molecularly disperse and/or finely dispersed liquid mixture,  
     (2) emulsifying the liquid mixture (1) in an aqueous medium in a dispersing unit, to give an aqueous emulsion of liquid particles,  
     (3) cooling the emulsion (2) so that a suspension of dimensionally stable particles is formed,  
     (4) isolating the dimensionally stable particles from the suspension (3)  
     or alternatively  
     (3) isolating the dimensionally stable particles directly from the emulsion (2);  
     and also processes for preparing them and their use as coating materials, adhesives, and sealing compounds or to prepare such compositions.

[0001] The present invention relates to novel powder coating materials,preparable by emulsification of liquid components. It also relates to aprocess for preparing novel powder coating materials by emulsificationof liquid components. The present invention additionally relates to theuse of the novel powder coating materials as coating materials,adhesives, and sealing compounds for coating, bonding, and sealing motorvehicle bodies and parts thereof, the interior and exterior of motorvehicles, the inside and outside of buildings, doors, windows, andfurniture, and for coating, bonding, and sealing in the context ofindustrial coating, particularly of small parts, coils, containers,packaging, electrical components, and white goods.

[0002] Powder coating materials in the form of aqueous suspensions(powder slurries) which are substantially free from organic solvents andmay be processed using liquid coating technologies, and processes forpreparing them by melt emulsification, are known from the German patentapplication DE 196 52 813 A1. In this known process, the binders, thecrosslinking agents, and any further additives are fed in the form ofviscous resin melts into the dispersing apparatus, in which they aredispersed finely in the liquid phase.

[0003] Alternatively, before their dispersing in the dispersingapparatus in the liquid state, the ingredients may first of all be mixedhomogeneously with one another and then, in a second step, dispersedfinely in the liquid phase. Thereafter, the resulting emulsion isconverted by cooling into a suspension containing solid, finely dividedparticles.

[0004] The isolation of the dispersed or suspended powder coatingparticles is not revealed in the German patent application.

[0005] According to column 7 lines 4 to 9 of DE 196 52 813 A1, use maybe made as stabilizers, dispersants or emulsifiers of short-chainamphiphilic polyacrylates prepared from acrylic acid, ethylhexylacrylate, hydroxyethyl acrylate and an anionic comonomer in lyotropicphase by means of transfer polymerization. The surface tension ofaqueous solutions of the emulsifiers at the critical micelleconcentration (CMC), however, is not specified.

[0006] Powder slurries prepared by melt emulsification are alsodescribed in the German patent applications DE 100 06 673.9 and DE 10018 581.9, unpublished at the priority date of the present specification.However, the resulting dispersed powder coating particles are notisolated and used as powder coating materials. Emulsifiers used includenonionic emulsifiers such as alkoxylated alkanols and polyols, phenolsand alkylphenols, or anionic emulsifiers such as alkali metal salts orammonium salts of alkanecarboxylic acids, alkanesulfonic acids, andsulfo acids of alkoxylated alkanols and polyols, phenols andalkylphenols. The surface tension of aqueous solutions of theemulsifiers at the critical micelle concentration (CMC), however, is notspecified.

[0007] A process for preparing powder coating materials by meltemulsification is known from the international patent application WO97/45476.

[0008] According to page 13 lines 5 to 20 of the international patentapplication, emulsifiers are used in the process. In the case of anaqueous phase, polyethylene glycol or polyvinyl alcohol is used. The keyfactor is that the emulsifiers have an anchor component which links theemulsifiers to the melt by means of physical adsorption or chemicalreaction. Examples of suitable anchor components are polar(meth)acrylate copolymers or the corresponding groups. The surfacetension of aqueous solutions of the emulsifiers at the critical micelleconcentration (CMC), however, is not specified.

[0009] For the known process it is important that the starting productsof the powder coating materials are melted in an extruder and mixed withone another. Still in the extruder, the resulting melt is mixed withwater.

[0010] A disadvantage of this known process is that the temperatures andthe residence times in the extruder must be set precisely in order toprevent premature crosslinking of binders and crosslinking agents.

[0011] Another process for preparing powder slurries by meltemulsification is known from the international patent application WO98/45356.

[0012] In this case ionic and nonionic emulsifiers (surfactants) areused. Ionic emulsifiers used include the in situ reaction products ofthe carboxyl-containing olefin copolymers used in the process withammonium hydroxide, triethanolamine, morpholine, anddimethylethanolamine. Preferred nonionic emulsifiers are alkylphenolthioxylates and ethylene oxide-propylene glycol copolymers. The surfacetension of aqueous solutions of the emulsifiers at the critical micelleconcentration (CMC), however, is not specified.

[0013] In the known process, the starting products are melted in anextruder and mixed with one another. The melt is subsequently introducedinto an autoclave, in which it is emulsified. The emulsions of themelted particles are thereafter stirred under pressure at temperaturesabove their melting point in order to make them spherical. According topage 4 lines 20 to 23 of the international patent application, at least30 seconds are required for this purpose.

[0014] A comparable process is disclosed by the American patent U.S.Pat. No. 4,056,653 A. According to column 2 lines 6 to 9 of the patent,at least 30 seconds are likewise required for said process step.

[0015] A disadvantage of this known process is that during thecomparatively long treatment time even slight changes in the processconditions may be accompanied by unwanted agglomeration of the meltedparticles.

[0016] The known processes described above for preparing powder coatingmaterials by melt emulsification have the further disadvantage that theextruders used as mixing equipment have a comparatively low efficiency,so that a comparatively high energy input is necessary in order toproduce a homogeneous melt. Moreover, the emulsifiers employed are onlyable to effect adequate stabilization of either the emulsified meltedparticles formed to start with or the suspended solid particles whichresult after cooling of the emulsion, but not both simultaneously. Withthe known processes, therefore, there is the risk that they will reactadversely even to slight variations in the process conditions and willnot produce powder coating materials that meet the specification.

[0017] The International Patent Application WO 00/17256 discloses yetanother process for preparing powder coating materials by meltemulsification. In this process the starting products, especially thebinders, are dispersed in fluids such as sulfur hexafluoride, fluoroformand/or xenon under supercritical or near-supercritical conditions. Thefluids are selected in such a way that the binders are slightly swollen.Moreover, the density of the fluids is adapted to the density of thestarting products by varying pressure and temperature. A prerequisitefor this process are the supercritical or near-supercritical conditions.The powder coating materials are recovered by pressure relief. Thisprocess necessitates expensive pressure-rated plant and the use ofcompounds which are known to induce an extremely high greenhouse gaseffect (cf. the international patent application on page 15 lines 28 and29).

[0018] The use of dispersions of copolymers preparable in aqueous mediaby single-stage or multistage free-radical copolymerization of

[0019] a) at least one olefinically unsaturated monomer and

[0020] b) at least one olefinically unsaturated monomer different thanthe olefinically unsaturated monomer (a) and of the general formula I

R¹R²C═CR³R⁴  (I)

[0021]  in which the radicals R¹, R², R³, and R⁴ each independently ofone another are hydrogen atoms or substituted or unsubstituted alkyl,cycloalkyl, alkylcycloalkyl cycloalkylalkyl, aryl, alkylaryl,cycloalkylaryl, arylalkyl or arylcycloalkyl radicals with the provisothat at least two of the variables R¹, R², R³ and R⁴ are substituted orunsubstituted aryl, arylalkyl or arylcycloalkyl radicals, especiallysubstituted or unsubstituted aryl radicals,

[0022] as binders in coating materials, especially aqueous basecoatmaterials (cf. the German patent application DE 199 30 665 A1),primer-surfacers and antistonechip primers (cf. the German patentapplication DE 199 30 067 A1), and clearcoat materials (cf. the Germanpatent application DE 199 30 664 A1) is known. Their use as stabilizers,emulsifiers or dispersants is not described in the patent applications.

[0023] It is an object of the present invention to find novel powdercoating materials preparable by an emulsification process, simply,reliably, rapidly and reproducibly with short residence times in theplant in question, said coating materials reliably meeting the givenspecifications.

[0024] It is a further object of the present invention to find a novelprocess for preparing powder coating materials which no longer has thedisadvantages of the prior art but which instead rapidly provideson-specification powder coating materials simply, reliably, andreproducibly with short residence times in the plant in question.

[0025] The invention accordingly provides the novel powder coatingmaterials preparable by

[0026] (1) mixing at least two liquid components comprising in each caseat least one liquid starting product in a static mixer, to give amolecularly disperse and/or finely dispersed liquid mixture,

[0027] (2) emulsifying the liquid mixture (1) in an aqueous medium in adispersing unit, to give an aqueous emulsion of liquid particles,

[0028] (3) cooling the emulsion (2) so that a suspension ofdimensionally stable particles is formed, and

[0029] (4) isolating the dimensionally stable particles from thesuspension (3)

[0030] or alternatively

[0031] (3) isolating the dimensionally stable particles directly fromthe emulsion (2).

[0032] In the text below, the novel powder coating materials arereferred to as “powder coating materials of the invention”.

[0033] The invention also provides the novel process for preparingpowder coating materials, which involves

[0034] (1) mixing at least two liquid components each comprising atleast one liquid starting product in the melted state in a static mixerto give a molecularly disperse or finely dispersed liquid mixture,

[0035] (2) emulsifying the liquid mixture (1) in a dispersing unit in anaqueous medium, to give an aqueous emulsion of liquid particles,

[0036] (3) cooling the emulsion (2), so that a suspension ofdimensionally stable particles is formed, and

[0037] (4) isolating the dimensionally stable particles (3) from thesuspension

[0038] or alternatively

[0039] (3) isolating the dimensionally stable particles directly fromthe emulsion (2).

[0040] In the text below, the novel process for preparing powder coatingmaterials is referred to as the “process of the invention”.

[0041] Further subject matter of the invention, processes and uses willemerge from the description.

[0042] In the light of the prior art it was surprising and unforeseeablefor the skilled worker that the object on which the present inventionwas based could be achieved by means of the process of the invention andthe powder coating materials of the invention. More surprising still wasthat it was the copolymers of the monomers (a) and (b), hitherto usedonly as binders, that had the properties required for them to beconsidered for the process of the invention. Surprising not least wasthe fact that, for a comparatively low energy input and very shortresidence times, the process of the invention could giveon-specification powder coating materials of the invention even withoutafter-treatment of the emulsified melted particles.

[0043] The starting products used in the process of the invention forpreparing the powder coating materials of the invention are selectedwith a view to the desired composition and the curing mechanism of thepowder coating materials of the invention.

[0044] The powder coating materials of the invention may be physicallycuring.

[0045] In the context of the present invention the term “physicalcuring” denotes the curing of a layer of particles of the powder coatingmaterials of the invention by filming, with linking within the coatingtaking place by looping of the polymer molecules of the binders(regarding the term cf. Römpp Lexikon Lacke und Druckfarben, GeorgThieme Verlag, Stuttgart, New York, 1998, “binders”, pages 73 and 74).Or else filming takes place by way of the coalescence of binderparticles (cf. Römpp Lexikon Lacke und Druckfarben, Georg Thieme Verlag,Stuttgart, New York, 1998, “curing”, pages 274 and 275). Normally, nocrosslinking agents are required for this purpose. If desired, physicalcuring may be assisted by atmospheric oxygen, by heat, or by exposure toactinic radiation.

[0046] The powder coating materials of the invention may be thermallycurable. In this case they may be self-crosslinking or externallycrosslinking.

[0047] In the context of the present invention the term“self-crosslinking” denotes the capacity of a binder to enter intocrosslinking reactions with itself. A prerequisite for this is that thebinders already contain both kinds of complementary reactive functionalgroups which are necessary for crosslinking. Externally crosslinking, onthe other hand, is a term used to refer to those coating materials inwhich one kind of the complementary reactive functional groups ispresent in the binder and the other kind is present in a curing agent orcrosslinking agent. For further details, refer to Rompp Lexikon Lackeund Druckfarben, Georg Thieme Verlag, Stuttgart, New York, 1998,“curing”, pages 274 to 276, especially page 275 bottom).

[0048] The powder coating materials of the invention may be curable withactinic radiation.

[0049] In this case curing takes place by way of groups containing bondswhich can be activated with actinic radiation. In the context of thepresent invention, actinic radiation means electromagnetic radiation,such as visible light, UV radiation or X-rays, especially UV radiation,and corpuscular radiation such as electron beams.

[0050] The powder coating materials of the invention may be curablethermally and with actinic radiation.

[0051] Where thermal curing and curing with actinic light are employedtogether for one powder coating material, the terms “dual cure” and“dual-cure powder coating material” are also used.

[0052] The powder coating materials of the invention are preferablyone-component (1K) systems.

[0053] In the context of the present invention, one-component (1K)systems are powder coating materials which cure thermally or boththermally and with actinic radiation and in which the binder and thecrosslinking agent are present alongside one another in the powdercoating particles. A prerequisite for this is that the two constituentscrosslink with one another only at relatively high temperatures and/oron exposure to actinic radiation.

[0054] The size of the dimensionally stable particles of the powdercoating materials of the invention may vary widely. Preferably, it isbetween 5 and 500, more preferably between 5 and 400, with particularpreference between 5 and 300, with very particular preference between 10and 200, and in particular between 10 and 100 μm. The average particlesize is preferably from 10 to 300, more preferably from 10 to 200, withparticular preference from 10 to 150, with very particular preferencefrom 10 to 100, and in particular from 10 to 50 μm. The particle sizedistribution may be narrow or broad. In the majority of cases a narrowparticle size distribution is of advantage, as described in the patentapplications and literature references EP 0 687 714 A1, DE 42 04 266 A1,DE 40 38 681 A1, P. G. de Lange and P. Selier, “Korngröβenverteilung undEigenschaften von elektrostatischen Spritzpulvern (1)— Fraktionierungdes Pulvers und Charakterisierung der Fraktionen” Farbe und Lack, vol.79, No. 5, 1973, pages 403 to 412, P. G. de Lange and P. Selier,“Korngröβenvertailung und Eigenschaften von elektrostatischenSpritzpulvern (2)—Verhalten der Pulverfraktionen beim Spritzen und nachdem Einbrennen” Farbe und Lack, vol. 79, No. 6, 1973, pages 509 to 517,and EP 0 536 791 A1.

[0055] In the context of the present invention, “dimensionally stable”means that under the customary and known conditions of the storage andapplication of powder coating materials or powder coating suspensionsthe particles undergo little if any agglomeration and/or breakdown intosmaller particles but instead substantially retain their original formeven under the influence of shear forces. The particles may be highlyviscous and/or solid. Preferably, the dimensionally stable particles aresolid.

[0056] The powder coating materials of the invention are preferably freefrom volatile organic compounds (VOCs), especially from organic solvents(cosolvents). In the context of the present invention this means thatthey have a residual VOC content of <1% by weight, preferably <0.5% byweight, and with particular preference <0.2% by weight. In accordancewith the invention it is of very particular advantage if the residualcontent is situated below the gas-chromatographic detection limit.

[0057] The process of the invention starts with the preparation of atleast two liquid components comprising at least one liquid startingproduct of the powder coating materials of the invention. The startingproducts may already be liquid at room temperature or may melt only athigher temperatures. The critical factor is that the starting productsare liquid at the process temperatures employed. Preferably, thestarting products are solid at room temperature.

[0058] The two liquid components may further comprise at least oneadditive which is not liquid at the process temperatures employed.However, a nonliquid additive of this kind must be capable ofhomogeneous distribution in the liquid components and must not disruptthe mixing processes in the static mixer or in the dispersing unit.

[0059] Preferably, one of the liquid components comprises the melt of atleast one of the binders described below. The binder melt may furthercomprise at least one of the additives described below. Preferably,these additives are liquid at the process temperatures employed and/orare present in homogeneous distribution in the melt.

[0060] Where the process of the invention is used to prepare powdercoating materials of the invention which cure physically or are curablewith actinic radiation, at least one of the further liquid componentspreferably comprises at least one of the additives described below whichis liquid at the process temperatures employed.

[0061] Where the process of the invention is used to prepare powdercoating materials of the invention which are curable thermally or boththermally and with actinic radiation, at least one of the further liquidcomponents preferably comprises the melt of at least one of thecrosslinking agents described below.

[0062] The preparation of the liquid components has no special featuresin terms of its method but instead takes place using the customary andknown techniques and apparatus for preparing liquids, especially polymermelts, such as extruders, stirred tanks, Taylor reactors, tube reactors,loop reactors, etc. The starting products, especially the binders, maybe prepared continuously in such apparatus and discharged continuouslyas a liquid.

[0063] The process temperatures are chosen so as not to exceed thedecomposition temperature of the starting product which decomposes themost readily. Preference is given to employing process temperatures offrom 50 to 250, preferably from 60 to 220, with particular preferencefrom 70 to 200, with very particular preference from 80 to 190, and inparticular from 90 to 180° C.

[0064] In the process of the invention the liquid components are firstof all supplied in the desired proportion to a customary and knownstatic mixer, and homogenized. Examples of suitable mixers are those ofthe Sulzer type, sold by Sulzer Chemtech GmbH.

[0065] The residence times of the liquid components in the static mixerare preferably from 0.5 to 20, more preferably from 1 to 18, withparticular preference from 1.5 to 16, with very particular preferencefrom 1.5 to 15, and in particular from 1.5 to 10 seconds.

[0066] The resulting liquid mixture comprises the liquid components inmolecularly dispersed form and/or finely dispersed in one another.

[0067] The liquid mixture is subsequently supplied to the dispersingunit in which it is emulsified in an aqueous medium to give an aqueousemulsion of liquid particles which may comprise constituents that arenot liquid at the process temperatures employed.

[0068] The aqueous medium preferably comprises essentially water orpreferably consists thereof. In this case the aqueous medium may includeminor amounts of the below-detailed additives and/or organic solventsand/or other dissolved solid, liquid or gaseous organic and/or inorganicsubstances of low and/or high molecular mass, provided they do notadversely affect the emulsification by, for example, causing the liquidparticles to agglomerate. In the context of the present invention, theterm “minor amount” means an amount which does not remove the aqueouscharacter of the aqueous medium.

[0069] The aqueous medium comprising additives may also comprise thepigment pastes or pigment preparations described below. Preferably, theaqueous medium comprises the copolymers which are described below andare based on the monomers (a) and (b), described below, as emulsifiers.

[0070] Dispersing units which can be used are all customary and knowndispersing units suitable for emulsifying liquids in aqueous media.

[0071] Examples of suitable dispersing units are inline dissolvershaving a rotor/stator construction, preferably toothed-ring dispersingunits particularly having at least one cylindrical arrangement of atleast two comminutor rings (stator and rotor) which are seated onholders, are in mutual embrace, and are rotatable in opposite directionsrelative to one another, the working gap produced by the relativemovement between stator and rotor having walls which extendnonparallelwise with respect to one another. In this case it is ofadvantage if the rotor rotates in the sense of an opening working gap.Examples of highly suitable toothed-ring dispersing units are describedin detail in the patent EP 0 648 537 A1. They are sold under the tradename K-Generatoren by Kinematica AG, Lucerne, Switzerland.

[0072] The ratio of disperse phase to continuous phase may vary widelyand is guided by the requirements of the specific case. Preferably, thevolume ratio of liquid mixture to aqueous medium is chosen so as to givean emulsion and a suspension with a solids content of at least 40% byweight, more preferably at least 45% by weight, with particularpreference at least 50% by weight, with very particular preference atleast 55% by weight, and in particular at least 60% by weight.

[0073] The residence times of the liquid mixture and of the aqueousphase or the emulsion in the dispersing unit is preferably from 0.5 to20, more preferably from 1 to 18, with particular preference from 1.5 to16, with very particular preference from 1.5 to 15, and in particularfrom 1.5 to 10 seconds.

[0074] Following emulsification, the resultant emulsified liquidparticles are cooled, thereby giving suspended, dimensionally stable, inparticular solid, particles. Preferably, the emulsion is cooledimmediately following its preparation without further aftertreatment. Inthis context it is preferred to employ the methods described in DE 19652 813 A1, column 8 lines 9 to 17.

[0075] As a result of the cooling procedure, the liquid particles becomedimensionally stable, and in particular become solid, thereby resultingin a suspension.

[0076] To prepare the powder coating materials of the invention, thesuspended dimensionally stable particles are isolated. Viewed in termsof its method, the isolation has no special features but instead takesplace with the aid of the customary and known equipment and techniquesas are employed, for example, for filtration, spray drying or freezedrying. Highly suitable techniques are drying techniques, using rotaryatomizers, pressure atomizers or pneumatic atomizers, such as aredescribed in the International Patent Application WO 99/01499, page 5line 24 to page 7 line 27 and page 27 line 16 to page 28 line 19.

[0077] Alternatively to the above-described variant of the isolation ofthe dimensionally stable particles from the suspensions, thedimensionally stable particles may also be recovered from the emulsionsof the liquid particles. This is done preferably by pressure release(flashing), in the course of which the emulsions cool as a result of theJoule-Thomson effect and at the same time the continuous phaseevaporates. For this purpose it is possible to employ customary andknown equipment comprising pressure vessels and evacuated vessels.

[0078] When preparing powder coating materials of the invention whichcan be crosslinked with actinic radiation it is advantageous to work inthe absence of actinic radiation.

[0079] The emulsified liquid particles and the suspended dimensionallystable particles comprise or consist of at least one binder.

[0080] The binder per se may be curable physically, thermally, withactinic radiation, and both thermally and with actinic radiation. Ingeneral it is present in the particles in an amount of from 5.0 to 100,preferably from 6.0 to 95, more preferably from 7.0 to 90, withparticular preference from 8.0 to 85, with very particular preferencefrom 9.0 to 80, and in particular from 10 to 80% by weight, based ineach case on the total amount of the particles.

[0081] The binder preferably has a glass transition temperature aboveroom temperature, more preferably from 30 to 80, with particularpreference from 40 to 70, with very particular preference from 40 to 60,and in particular about 50° C. (measured by means of DifferentialScanning Calorimetry (DSC)).

[0082] The molecular weight of the binder may vary very widely. Inaccordance with the invention it is preferred not to choose too high abinder molecular weight, since otherwise problems may occur in thecourse of its filming. Preferably, the number average molecular weightis from 500 to 30,000, more preferably from 500 to 25,000, withparticular preference from 500 to 20,000, with very particularpreference from 500 to 15,000, and in particular from 500 to 10,000.

[0083] The binders are oligomeric and polymeric resins. Oligomers areresins containing at least 2 to 15 monomer units in their molecule. Inthe context of the present invention, polymers are resins containing atleast 10 repeating monomer units in their molecule. For further detailsof these terms, refer to Rompp Lexikon Lacke und Druckfarben, GeorgThieme Verlag, Stuttgart, New York, 1998, “oligomers”, page 425.

[0084] It is of advantage if the minimum film formation temperature ofthe binders is in the region of their glass transition temperature Tgand in particular at at least 25° C. The minimum film formationtemperature may be determined by drawing the aqueous dispersion of thebinder down onto a glass plate using a coating bar and heating thedrawdown in a gradient oven. The temperature at which the pulverulentlayer forms a film is referred to as the minimum film formationtemperature. For further details, refer to Römpp Lexikon Lacke undDruckfarben, Georg Thieme Verlag, Stuttgart, New York, 1998, “minimumfilm formation temperature”, page 391.

[0085] Examples of suitable binders are random, alternating and/orblock, linear and/or branched and/or comb addition (co)polymers ofolefinically unsaturated monomers, or polyaddition resins and/orpolycondensation resins. For further details of these terms, refer toRömpp Lexikon Lacke und Druckfarben, Georg Thieme Verlag, Stuttgart, NewYork, 1998, page 457, “polyaddition” and “polyaddition resins(polyadducts)”, and pages 463 and 464, “polycondensates”,“polycondensation” and “polycondensation resins”, and also pages 0.73and 74, “binders”.

[0086] Examples of suitable addition (co)polymers are (meth)acrylate(co)polymers or partially saponified polyvinyl esters, especially(meth)acrylate copolymers.

[0087] Examples of suitable polyaddition resins and/or polycondensationresins are polyesters, alkyds, polyurethanes, polylactones,polycarbonates, polyethers, epoxy resin-amine adducts, polyureas,polyamides, polyimides, polyester-polyurethanes, polyether-polyurethanesor polyester-polyether-polyurethanes, especiallypolyester-polyurethanes.

[0088] Of these binders, the (meth)acrylate (co)polymers have particularadvantages and are therefore used with particular preference.

[0089] The self-crosslinking binders of the thermally curable powdercoating materials of the invention contain reactive functional groupswhich are able to enter into crosslinking reactions with groups of theirown kind or with complementary reactive functional groups.

[0090] The externally crosslinking binders contain reactive functionalgroups which are able to enter into crosslinking reactions withcomplementary reactive functional groups that are present incrosslinking agents.

[0091] Examples of suitable complementary reactive functional groups foruse in accordance with the invention are summarized in the followingoverview. In the overview, the variable R stands for an acylic or cyclicaliphatic radical, an aromatic radical and/or an aromatic-aliphatic(araliphatic) radical; the variables R′ and R″ stand for identical ordifferent aliphatic radicals or are linked with one another to form analiphatic or heteroaliphatic ring.

[0092] Overview: Examples of Complementary Functional Groups Binder andCrosslinking agent or Crosslinking agent and Binder —SH —C(O)—OH —NH₂—C(O)—O—C(O)— —OH —NCO —O—(CO)—NH—(CO)—NH₂ —NH—C(O)—OR —O—(CO)—NH₂—CH₂—OH >NH —CH₂—O—R —NH—CH₂—O—R —NH—CH₂—OH —N(—CH₂—O—R)₂—NH—C(O)—CH(—C(O)OR)₂ —NH—C(O)—CH(—C(O)OR)(—C(O)—R) —NH—C(O)—NR′R″>Si(OR)₂

—C(O)—OH

—C(O)—N(CH₂—CH₂—OH)₂

[0093] The selection of the respective complementary groups is guided onthe one hand by the consideration that, during the preparation, storage,application, and melting of the powder coating materials of theinvention, they should not enter into any unwanted reactions,particularly no premature crosslinking, and/or, where appropriate, mustnot disrupt or inhibit curing with actinic radiation, and on the otherby the temperature range within which crosslinking is to take place.

[0094] In the case of the powder coating materials of the invention itis preferred to employ crosslinking temperatures from 60 to 180° C. Itis therefore preferred to employ binders containing thio, hydroxyl,N-methylolamino, N-alkoxymethylamino, imino, carbamate, allophanateand/or carboxyl groups, preferably hydroxyl or carboxyl groups, on theone hand and preferred to employ crosslinking agents containinganhydride, carboxyl, epoxy, blocked isocyanate, urethane, methylol,methylol ether, siloxane, carbonate, amino, hydroxyl and/orbeta-hydroxyalkyl amide groups, preferably epoxy,beta-hydroxyalkylamide, blocked isocyanate, urethane oralkoxymethylamino groups, on the other.

[0095] In the case of self-crosslinking powder coating materials of theinvention, the binders include in particular methylol, methylol etherand/or N-alkoxymethylamino groups.

[0096] Complementary reactive functional groups particularly suitablefor use in the powder coating materials of the invention are

[0097] carboxyl groups on the one hand and epoxide groups and/orbeta-hydroxyalkylamide groups on the other, and

[0098] hydroxyl groups on the one hand and blocked isocyanate, urethaneor alkoxymethylamino groups on the other.

[0099] The functionality of the binders in respect of the reactivefunctional groups described above may vary very widely and depends inparticular on the desired crosslinking density and/or on thefunctionality of the crosslinking agents employed in each case. In thecase of carboxyl-containing binders, for example, the acid number ispreferably from 10 to 100, more preferably from 15 to 80, withparticular preference from 20 to 75, with very particular preferencefrom 25 to 70, and, in particular, from 30 to 65 mg KOH/g.Alternatively, in the case of hydroxyl-containing binders, the OH numberis preferably from 15 to 300, more preferably from 20 to 250, withparticular preference from 25 to 200, with very particular preferencefrom 30 to 150, and, in particular, from 35 to 120 mg KOH/g.Alternatively, in the case of binders containing epoxide groups, theepoxide equivalent weight is preferably from 400 to 2500, morepreferably from 420 to 2200, with particular preference from 430 to2100, with very particular preference from 440 to 2000, and, inparticular, from 440 to 1900.

[0100] The complementary functional groups described above can beincorporated into the binders in accordance with the customary and knownmethods of polymer chemistry. This can be done, for example, byincorporating monomers which carry the corresponding reactive functionalgroups, and/or with the aid of polymer-analogous reactions.

[0101] Examples of suitable olefinically unsaturated monomers containingreactive functional groups are the monomers (a) described below,especially

[0102] (i) monomers which carry at least one hydroxyl, amino,alkoxymethylamino, carbamate, allophanate or imino group per molecule,such as

[0103] hydroxyalkyl esters of acrylic acid, methacrylic acid or anotheralpha,beta-olefinically unsaturated carboxylic acid, which are derivedfrom an alkylene glycol which is esterified with the acid, or which areobtainable by reacting the alpha,beta-olefinically unsaturatedcarboxylic acid with an alkylene oxide such as ethylene oxide orpropylene oxide, especially hydroxyalkyl esters of acrylic acid,methacrylic acid, ethacrylic acid, crotonic acid, maleic acid, fumaricacid or itaconic acid, in which the hydroxyalkyl group contains up to 20carbon atoms, such as 2-hydroxyethyl, 2-hydroxypropyl, 3-hydroxypropyl,3-hydroxybutyl, 4-hydroxybutyl acrylate, methacrylate, ethacrylate,crotonate, maleate, fumarate or itaconate; or hydroxycycloalkyl esterssuch as 1,4-bis. (hydroxymethyl)cyclohexane,octahydro-4,7-methano-1H-indenedimethanol or methylpropanediolmonoacrylate, monomethacrylate, monoethacrylate, monocrotonate,monomaleate, monofumarate or monoitaconate; reaction products of cyclicesters, such as epsilon-caprolactone and these hydroxyalkyl orhydroxycycloalkyl esters;

[0104] olefinically unsaturated alcohols such as allyl alcohol;

[0105] polyols such as trimethylolpropane monoallyl or diallyl ether orpentaerythritol monoallyl, diallyl or triallyl ether;

[0106] reaction products of acrylic acid and/or methacrylic acid withthe glycidyl ester of an alpha-branched monocarboxylic acid having 5 to18 carbon atoms per molecule, especially a Versatic® acid, or instead ofthe reaction product an equivalent amount of acrylic and/or methacrylicacid, which is then reacted during or after the polymerization reactionwith the glycidyl ester of an alpha-branched monocarboxylic acid having5 to 18 carbon atoms per molecule, especially a Versatic® acid;

[0107] aminoethyl acrylate, aminoethyl methacrylate, allylamine orN-methyliminoethyl acrylate;

[0108] N,N-di(methoxymethyl)aminoethyl acrylate or methacrylate orN,N-di(butoxymethyl)aminopropyl acrylate or methacrylate;

[0109] (meth)acrylamides such as (meth)acrylamide, N-methyl-,N-methylol-, N,N-dimethylol-, N-methoxymethyl-, N,N-di(methoxymethyl)-,N-ethoxymethyl- and/or N,N-di(ethoxyethyl)(meth)acrylamide;

[0110] acryloyloxy- or methacryloyloxyethyl, -propyl or -butyl carbamateor allophanate; further examples of suitable monomers containingcarbamate groups are described in the patents U.S. Pat. No. 3,479,328,U.S. Pat. No. 3,674,838, U.S. Pat. No. 4,126,747, U.S. Pat. No.4,279,833 and U.S. Pat. No. 4,340,497;

[0111] (ii) monomers (a3) which carry at least one acid group permolecule, such as

[0112] acrylic acid, methacrylic acid, beta-carboxyethyl acrylate,ethacrylic acid, crotonic acid, maleic acid, fumaric acid or itaconicacid;

[0113] olefinically unsaturated sulfonic or phosphonic acids or theirpartial esters;

[0114] mono(meth)acryloyloxyethyl maleate, succinate or phthalate; or

[0115] vinylbenzoic acid (all isomers), alpha-methylvinylbenzoic acid(all isomers) or vinylbenzenesulfonic acid (all isomers);

[0116] (iii) monomers containing epoxide groups, such as the glycidylester of acrylic acid, methacrylic acid, ethacrylic acid, crotonic acid,maleic acid, fumaric acid or itaconic acid, or allyl glycidyl ether.

[0117] They are preferably used to prepare the inventively preferred(meth)acrylate copolymers, especially the ones containing glycidylgroups.

[0118] More highly functional monomers of the type described above aregenerally used in minor amounts. For the purposes of the presentinvention, minor amounts of higher-functional monomers are those amountswhich do not lead to crosslinking or gelling of the addition copolymers,in particular of the (meth)acrylate copolymers, unless the specificdesire is to prepare crosslinked polymeric microparticles.

[0119] Examples of suitable monomer units for introducing reactivefunctional groups into polyesters or polyester-polyurethanes are2,2-dimethylolethyl- or propylamine blocked with a ketone, the resultingketoxime group being hydrolyzed again following incorporation; orcompounds containing two hydroxyl groups or two primary and/or secondaryamino groups and also at least one acid group, in particular at leastone carboxyl group and/or at least one sulfonic acid group, such asdihydroxypropionic acid, dihydroxysuccinic acid, dihydroxybenzoic acid,2,2-dimethylolacetic acid, 2,2-dimethylolpropionic acid,2,2-dimethylolbutyric acid, 2,2-dimethylolpentanoic acid,2,2-diaminovaleric acid, 3,4-diaminobenzoic acid,2,4-diaminotoluenesulfonic acid or 2,4-diaminodiphenyl ether sulfonicacid.

[0120] One example of introducing reactive functional groups by way ofpolymer-analogous reactions is the reaction of hydroxyl-containingresins with phosgene, resulting in resins containing chloroformategroups, and the polymer-analogous reaction of thechloroformate-functional resins with ammonia and/or primary and/orsecondary amines to give resins containing carbamate groups. Furtherexamples of suitable methods of this kind are known from the patentsU.S. Pat. No. 4,758,632 A1, U.S. Pat. No. 4,301,257 A1 and U.S. Pat. No.2,979,514 A1. Moreover, it is possible to introduce carboxyl groups bypolymer-analogous reaction of hydroxyl groups with carboxylicanhydrides, such as maleic anhydride or phthalic anhydride.

[0121] The binders of the dual-cure powder slurries and powder coatingmaterials of the invention further comprise on average per molecule atleast one, preferably at least two, group(s) having at least one bondthat can be activated with actinic radiation.

[0122] For the purposes of the present invention, a bond that can beactivated with actinic radiation is a bond which on exposure to actinicradiation becomes reactive and, with other activated bonds of its kind,enters into addition polymerization reactions and/or crosslinkingreactions which proceed in accordance with free-radical and/or ionicmechanisms. Examples of suitable bonds are carbon-hydrogen single bondsor carbon-carbon, carbon-oxygen, carbon-nitrogen, carbon-phosphorus orcarbon-silicon single bonds or double bonds. Of these, the carbon-carbondouble bonds are particularly advantageous and are therefore used withvery particular preference in accordance with the invention. For thesake of brevity, they are referred to below as double bonds.

[0123] Accordingly, the group which is preferred in accordance with theinvention comprises one double bond or two, three or four double bonds.If more than one double bond is used, the double bonds can beconjugated. In accordance with the invention, however, it is ofadvantage if the double bonds are present in isolation, in particulareach being present terminally, in the group in question. It is ofparticular advantage in accordance with the invention to use two doublebonds or, in particular, one double bond.

[0124] The dual-cure binder contains on average at least one of theabove-described groups that can be activated with actinic radiation.This means that the functionality of the binder in this respect isintegral, i.e., for example, is two, three, four, five or more, ornonintegral, i.e., for example, is from 2.1 to 10.5 or more. Thefunctionality chosen depends on the requirements imposed on therespective pigmented dual-cure powder slurries and powder coatingmaterials of the invention.

[0125] If more than one group that can be activated with actinicradiation is used on average per molecule, the groups are structurallydifferent from one another or of the same structure.

[0126] If they are structurally different from one another, this means,in the context of the present invention, that use is made of two, three,four or more, but especially two, groups that can be activated byactinic radiation, these groups deriving from two, three, four or more,but especially two, monomer classes.

[0127] Examples of suitable groups are (meth)acrylate, ethacrylate,crotonate, cinnamate, vinyl ether, vinyl ester, dicyclopentadienyl,norbornenyl, isoprenyl, isopropenyl, allyl or butenyl groups;dicyclopentadienyl, norbornenyl, isoprenyl, isopropenyl, allyl orbutenyl ether groups; or dicyclopentadienyl, norbornenyl, isoprenyl,isopropenyl, allyl or butenyl ester groups, but especially acrylategroups.

[0128] Preferably, the groups are attached to the respective parentstructures of the binders via urethane, urea, allophanate, ester, etherand/or amide groups, but in particular via ester groups. Normally, thisoccurs as a result of customary and known polymer-analogous reactionssuch as, for instance, the reaction of pendant glycidyl groups with theolefinically unsaturated monomers described above that contain an acidgroup, of pendant hydroxyl groups with the halides of these monomers, ofhydroxyl groups with isocyanates containing double bonds such as vinylisocyanate, methacryloyl isocyanate and/or1-(1-isocyanato-1-methylethyl)-3-(1-methylethenyl)benzene (TMI® from thecompany CYTEC), or of isocyanate groups with the above-describedhydroxyl-containing monomers.

[0129] Alternatively, in the particles it is possible to employ mixturesof purely thermally curable binders and binders that are curable purelywith actinic radiation.

[0130] The material composition of the binders does not basically haveany special features; rather, suitable binders include

[0131] all the binders envisaged for use in powder clearcoat slurriescurable thermally and/or with actinic radiation that are described inthe U.S. Pat. No. 4,268,542 A1 or U.S. Pat. No. 5,379,947 A1 and in thepatent applications DE 27 10 421 A1, DE 1.95 40 977 A1, DE 195 18 392A1, DE 196 17 086 A1, DE 196 18 657 A1, DE 196 52 813 A1, DE 196 17 086A1, DE 198 14 471 A1, DE 196 13 547 A1, DE 198 41 842 A1 or DE 198 41408 A1, in the German patent applications DE 199 08 018.6 or DE 199 08013.5, unpublished at the priority date of the present specification, orin the European patent EP 0 652 264 A1;

[0132] all the binders envisaged for use in dual-cure clearcoats thatare described in the patent applications DE 198 35 296 A1, DE 197 36 083A1 or DE 198 41 842 A1; or

[0133] all the binders envisaged for use in thermally curable powderclearcoats and described in the German patent application DE 42 22 194A1, in the product information bulletin from BASF Lacke+Farben AG,“Pulverlacke”, 1990, or in the BASF Coatings AG brochure “Pulverlacke,Pulverlacke für industrielle Anwendungen”, January 2000.

[0134] Suitable additional binders for the dual-cure powder slurries andpowder coating materials, are the binders envisaged for use inUV-curable clearcoats and powder clearcoats and described in Europeanpatent applications EP 0 928 800 A1, EP 0 636 669 A1, EP 0 410 242 A1,EP 0 783 534 A1, EP 0 650 978 A1, EP 0 650 979 A1, EP 0 650 985 A1, EP 0540 884 A1, EP 0 568 967 A1, EP 0 054 505 A1 or EP 0 002 866 A1, in theGerman patent applications DE 197 09 467 A1, DE 42 03 278 A1, DE 33 16593 A1, DE 38 36 370 A1, DE 24 36 186 A1 or DE 20 03 579 B1, in theinternational patent applications WO 97/46549 or WO 99/14254, or in theAmerican patents U.S. Pat. No. 5,824,373 A1, U.S. Pat. No. 4,675,234 A1,U.S. Pat. No. 4,634,602 A1, U.S. Pat. No. 4,424,252 A1, U.S. Pat. No.4,208,313 A1, U.S. Pat. No. 4,163,810 A1, U.S. Pat. No. 4,129,488 A1,U.S. Pat. No. 4,064,161 A1 or U.S. Pat. No. 3,974,303 A1.

[0135] The preparation of the binders also has no special features interms of its method but instead takes place with the aid of thecustomary and known methods of polymer chemistry, as described indetail, for example, in the patent documents cited above.

[0136] Further examples of suitable preparation processes for(meth)acrylate copolymers are described in the European patentapplication EP 0 767 185 A1, in the German patents DE 22 14 650 B1 or DE27 49 576 B1, and in the American patents U.S. Pat. No. 4,091,048 A1,U.S. Pat. No. 3,781,379 A1, U.S. Pat. No. 5,480,493 A1, U.S. Pat. No.5,475,073 A1 or U.S. Pat. No. 5,534,598 A1, or in the standard workHouben-Weyl, Methoden der organischen Chemie, 4th edition, volume 14/1,pages 24 to 255, 1961. Suitable reactors for the copolymerizationinclude the customary and known stirred tanks, stirred tank cascades,tube reactors, loop reactors or Taylor reactors, as described forexample in the patents and patent applications DE 1 071 241 B1, EP 0 498583 A1, and DE 198 28 742 A1 or in the article by K. Kataoka in ChemicalEngineering Science, volume 50, No. 9, 1995, pages 1409 to 1416.

[0137] The preparation of suitable polyesters and alkyd resins are alsodescribed, for example, in the standard work Ullmanns Encyklopadie dertechnischen Chemie, 3rd edition, Volume 14, Urban & Schwarzenberg,Munich, Berlin, 1963, pages 80 to 89 and pages 99 to 105, and also inthe following books: “Résines Alkydes-Polyesters” by J. Bourry, Dunod,Paris, 1952, “Alkyd 25. Resins” by C. R. Martens, Reinhold PublishingCorporation, New York, 1961, and also “Alkyd Resin Technology” by T. C.Patton, Interscience Publishers, 1962.

[0138] The preparation of suitable polyurethanes and/or acrylatedpolyurethanes is described, for example, in the patent applications EP 0708 788 A1, DE 44 01 544 A1, and DE 195 34 361 A1.

[0139] Of these binders, the (meth)acrylate copolymers containingepoxide groups, having an epoxide equivalent weight of preferably from400 to 2500, more preferably from 420 to 2200, with particularpreference from 430 to 2100, with very particular preference from 440 to2000, and, in particular, from 440 to 1900, a number-average molecularweight (determined by gel permeation chromatography using a polystyrenestandard) of preferably from 2000 to 20,000 and in particular from 3000to 10,000, and a glass transition temperature (T_(g)) of preferably from30 to 80, more preferably from 40 to 70 and in particular from 40 to 60°C. (measured by means of differential scanning calorimetry (DSC)), assuitable in particular for use in thermally curable powder clearcoatslurries (see above) and as described, furthermore, in the patents andpatent applications EP 0 299 420 A1, DE 22 14 650 B1, DE 27 49 576 B1,U.S. Pat. No. 4,091,048 A1 and U.S. Pat. No. 3,781,379 A1, areparticularly advantageous and are used with particular preference.

[0140] The externally crosslinking powder coating materials of theinvention curable thermally or both thermally and with actinicradiation, and/or the particles used for their preparation, include atleast one crosslinking agent containing the reactive functional groupscomplementary to the reactive functional groups of the binders. Theskilled worker will therefore easily be able to select the crosslinkingagents suitable for the case in hand.

[0141] In the process of the invention, the crosslinking agents arepreferably supplied to the static mixer in the form of a separate liquidcomponent, in particular a melt, or in a separate liquid component, inparticular a melt. The ratio of binder melt to crosslinking agent meltis guided by the desired ratio of complementary reactive functionalgroups in the powder coating materials of the invention.

[0142] Examples of suitable crosslinking agents are

[0143] amino resins, as described for example in Römpp Lexikon Lacke undDruckfarben, Georg Thieme Verlag, 1998, page 29, “amino resins”, in thetextbook “Lackadditive” [Additives for coatings] by Johan Bieleman,Wiley-VCH, Weinheim, New York, 1998, pages 242 ff., in the book “Paints,Coatings and Solvents”, second, completely revised edition, edited by D.Stoye and W. Freitag, Wiley-VCH, Weinheim, New York, 1998, pages 80 ff.,in the patents U.S. Pat. No. 4,710,542 A, and EP 0 245 700 A1, and inthe article by B. Singh and coworkers, “Carbamylmethylated Melamines,Novel Crosslinkers for the Coatings Industry”, in Advanced OrganicCoatings Science and Technology Series, 1991, Volume 13, pages 193 to207;

[0144] carboxyl-containing compounds or resins, as described for examplein the patent DE 196 52 813 A1 or 198 41 408 A1, especially1,12-dodecanedioic acid (1,10-decanedicarboxylic acid);

[0145] resins or compounds containing epoxy groups, as described forexample in the patents EP 0 299 420 A1, DE 22 14 650 B1, DE 27 49 576B1, us 4,091,048 A1, and U.S. Pat. No. 3,781,379 A1;

[0146] blocked polyisocyanates, as described for example in the patents'U.S. Pat. No. 4,444,954 A1, DE 196 17 086 A1, DE 196 31 269 A1, EP 0 004571 A1, and EP 0 582 051 A1;

[0147] beta-hydroxyalkylamides such asN,N,N′,N′-tetrakis(2-hydroxyethyl)adipamide orN,N,N′,N′-tetrakis(2-hydroxypropyl)adipamide; and/or

[0148] tris(alkoxycarbonylamino)triazines, as described in the patentsU.S. Pat. No. 4,939,213 A1, U.S. Pat. No. 5,084,541 A1, U.S. Pat. No.5,288,865 A1 and EP 0 604 922 A1.

[0149] The amount of the crosslinking agents in the particles maylikewise vary very widely and is guided by the requirements of eachindividual case, in particular by the number of reactive functionalgroups present and by the target crosslinking density of the coatings,adhesive films, and seals produced from the powder coating materials ofthe invention. The amount is preferably from 1 to 50, more preferablyfrom 2 to 45, with particular preference from 3 to 40, with veryparticular preference from 4 to 35, and in particular from 5 to 0.30% byweight, based on the solids of the powder coating materials of theinvention.

[0150] Depending on the end use of the powder coating materials of theinvention, they may comprise color and/or effect pigments, fluorescentpigments, electrically conductive and/or magnetically shieldingpigments, metal powders, organic and inorganic, transparent or opaquefillers and/or nanoparticles (referred to collectively as “pigments”below). The pigments are used when the powder coating materials of theinvention are to be used as pigmented coating materials, adhesives, andsealing compounds.

[0151] In the process of the invention they are preferably dispersedinto the aqueous media in the form of pigment pastes or pigmentpreparations (cf. Römpp Lexikon Lacke und Druckfarben, Georg ThiemeVerlag, Stuttgart, New York, 1998, “pigment preparations”, page 452)or—as already mentioned above—they constitute the aqueous media.Preferably, they comprise the emulsifiers described below.

[0152] In one embodiment of the process of the invention, the emulsifiedor suspended particles comprise at least one pigment; i.e., the totalamount of the pigments used is present in and/or on the particles.

[0153] In another embodiment of the process of the invention, theemulsified or suspended particles contain no pigment; i.e., all of thepigments are present in the form of a separate solid phase. Regardingtheir particle size, the comments made above apply analogously.

[0154] In yet another embodiment of the process of the invention, theemulsified or suspended particles comprise, in the sense mentionedabove, a portion of the pigments used, while the other portion of thepigments is present in the form of a separate solid phase. In this case,the fraction present in the particles may comprise the majority, i.e.,more than 50%, of the pigments used. It is, however, also possible forless than 50% to be present in and/or on the particles. Regarding theparticle sizes, the comments made above apply analogously here as well.

[0155] Which variant of the process of the invention is given preferencein preparing the pigmented powder coating materials of the inventiondepends in particular on the nature of the pigments and their functions.Particular preference is given to employing the variant in which all, orthe predominant fraction, of the pigments are/is present in and/or onthe emulsified and suspended particles.

[0156] Examples of suitable effect pigments are metal flake pigmentssuch as commercially customary aluminum bronzes, aluminum bronzeschromated in accordance with DE 36 36 183 A1, and commercially customarystainless steel bronzes, and also nonmetallic effect pigments, such aspearlescent pigments and interference pigments, platelet-shaped effectpigments based on iron oxide, which has a shade ranging from pink tobrownish red, liquid-crystalline effect pigments. For further details,reference is made to Römpp Lexikon Lacke und Druckfarben, Georg ThiemeVerlag, 1998, page 176, “effect pigments” and pages 380 and 381, “metaloxide-mica pigments” to “metal pigments”, and to the patent applicationsand patents DE 36 36 156 A1, DE 37 18 446 A1, DE 37 19 804 A1, DE 39 30601 A1, EP 0 068 311 A1, EP 0 264 843 A1, EP 0 265 820 A1, EP 0 283 852A1, EP 0 293 746 A1, EP 0 417 567 A1, U.S. Pat. No. 4,828,826 A, andU.S. Pat. No. 5,244,649 A.

[0157] Examples of suitable inorganic color pigments are white pigmentssuch as titanium dioxide, zinc white, zinc sulfide or lithopones; blackpigments such as carbon black, iron manganese black or spinel black;chromatic pigments such as chromium oxide, chromium oxide hydrate green,cobalt green or ultramarine green, cobalt blue, ultramarine blue ormanganese blue, ultramarine violet or cobalt violet and manganeseviolet, red iron oxide, cadmium sulfoselenide, molybdate red orultramarine red; brown iron oxide, mixed brown, spinel phases andcorundum phases or chrome orange; or yellow iron oxide, nickel titaniumyellow, chrome titanium yellow, cadmium sulfide, cadmium zinc sulfide,chrome yellow or bismuth vanadate.

[0158] Examples of suitable organic color pigments are monoazo pigments,disazo pigments, anthraquinone pigments, benzimidazole pigments,quinacridone pigments, quinophthalone pigments, diketopyrrolopyrrolepigments, dioxazine pigments, indanthrone pigments, isoindolinepigments, isoindolinone pigments, azomethine pigments, thioindigopigments, metal complex pigments, perinone pigments, perylene pigments,phthalocyanine pigments or aniline black.

[0159] For further details, reference is made to Römpp Lexikon Lacke undDruckfarben, Georg Thieme Verlag, 1998, pages 180 and 181, “iron bluepigments” to “black iron oxide”, pages 451 to 453, “pigments” to“pigment volume concentration”, page 563, “thioindigo pigments”, page567, “titanium dioxide pigments”, pages 400 and 467, “naturallyoccurring pigments”, page 459 “polycyclic pigments”, page 52,“azomethine pigments”, “azo pigments”, and page 379, “metal complexpigments”.

[0160] Examples of (daylight-)fluorescent pigments are bis(azomethine)pigments.

[0161] Examples of suitable electrically conductive pigments aretitanium dioxide/tin oxide pigments.

[0162] Examples of magnetically shielding pigments are pigments based oniron oxides or chromium dioxide.

[0163] Examples of suitable metal powders are powders of metals andmetal alloys comprising aluminum, zinc, copper, bronze or brass.

[0164] Examples of suitable organic and inorganic fillers are chalk,calcium sulfates, barium sulfate, silicates such as talc, mica orkaolin, silicas, oxides such as aluminum hydroxide or magnesiumhydroxide, or organic fillers such as polymer powders, especially ofpolyacrylonitrile or polyamide. For further details, reference is madeto Römpp Lexikon Lacke und Druckfarben, Georg Thieme Verlag, 1998, pages250 ff., “fillers”.

[0165] Preference is given to employing mica and talc when the intentionis to improve the scratch resistance of the coatings produced from thepowder slurries of the invention.

[0166] Moreover, it is advantageous to use mixtures of platelet-shapedinorganic fillers such as talc or mica and non-platelet-shaped inorganicfillers such as chalk, dolomite, calcium sulfates or barium sulfate,since by this means the viscosity and rheology may be adjusted veryeffectively.

[0167] Examples of suitable transparent fillers are those based onsilica, alumina or zirconium oxide.

[0168] Suitable nanoparticles are selected from the group consisting ofhydrophilic and hydrophobic, especially hydrophilic, nanoparticles basedon silica, alumina, zinc oxide, zirconium oxide, and the polyacids andheteropoly acids of transition metals, preferably of molybdenum andtungsten, having a primary particle size >50 nm, preferably from 5 to 50nm, in particular from 10 to 30 nm. Preferably, the hydrophilicnanoparticles have no flatting effect. Particular preference is given tousing nanoparticles based on silica.

[0169] Very particular preference is given to using hydrophilicpyrogenic silicas whose agglomerates and aggregates have a catenatedstructure, and which are preparable by the flame hydrolysis of silicontetrachloride in an oxyhydrogen flame. They are sold, for example, byDegussa under the brand name Aerosil®. Very particular preference isalso given to precipitated waterglasses, such as nanohectorites, whichare sold, for example, by Südchemie under the brand name Optigel® or byLaporte under the brand name Laponite®.

[0170] Pigment pastes or pigment preparations may contain a particularlyhigh level of nanoparticles when the emulsifiers described below andused with particular preference are employed, this being a furthervaluable advantage of the emulsifiers to be used with particularpreference.

[0171] In addition to the above-described pigments or instead of thesethe powder coating materials of the invention may comprise molecularlydispersed organic dyes.

[0172] In the context of the process of the invention, the organic dyesmay be supplied to the static mixer in the form of separate liquidcomponents or in separate liquid components or in the binder and/orcrosslinking agent melts and/or may be present in the above-describedaqueous media.

[0173] The molecularly dispersed dyes may be present in the process ofthe invention either in the emulsified or suspended particles or in thecontinuous phase, i.e., the continuous, i.e., aqueous, medium.Alternatively, they may be present in the particles and in thecontinuous phase. In this case, the fraction that is present in theparticles may comprise the majority, i.e., more than 50%, of the organicdyes used. However, less than 50% may be present, alternatively, in theparticles. The distribution of the organic dyes between the phases maycorrespond to the thermodynamic equilibrium resulting from thesolubility of the organic dyes in the phases. However, the distributionmay also be far removed from the thermodynamic equilibrium. The dyes arepreferably present only in the emulsified and suspended particles.

[0174] Suitable organic dyes are all those soluble in the sense outlinedabove in the powder coating materials of the invention. Lightfastorganic dyes are highly suitable. Lightfast organic dyes having littleor no tendency to migrate from the coatings, adhesive films, and sealsproduced from the powder coating materials of the invention areespecially suitable. The migration tendency may be estimated by theskilled worker on the basis of his or her general knowledge of the artand/or determined with the aid of simple preliminary rangefinding tests,as part of tinting tests, for example.

[0175] The amount of the molecularly dispersed organic dyes in thepowder coating materials of the invention may vary extremely widely andis guided primarily by the color and by the shade that is to beestablished, and also by the amount of any pigments present.

[0176] The pigmented and unpigmented powder coating materials of theinvention may comprise at least one further additive. In the context ofthe process of the invention, said additive may be supplied to thestatic mixer as a separate liquid component or in a separate liquidcomponent. Preferably, the additive is incorporated into the emulsifiedand suspended particles by way of the binder melts.

[0177] Examples of suitable additives which may be present both in thepigmented and nonpigmented powder coating materials of the invention areUV absorbers, antioxidants, light stabilizers, free-radical scavengers,devolatilizers, wetting agents, slip additives, polymerizationinhibitors, crosslinking catalysts, thermolabile free-radicalinitiators, photoinitiators, thermally curable reactive diluents,reactive diluents curable with actinic radiation, adhesion promoters,leveling agents, film-forming auxiliaries, flame retardants, corrosioninhibitors, free-flow aids, waxes, siccatives, biocides and/or flattingagents.

[0178] Examples of suitable thermally curable reactive diluents arepositionally isomeric diethyloctanediols or hydroxyl-containinghyperbranched compounds or dendrimers, as described in the German patentapplications DE 198 09 643 A1, DE 198 40 605 A1 and DE 198 05 421 A1.

[0179] Examples of suitable reactive diluents curable with actinicradiation are those described in Römpp Lexikon Lacke und Druckfarben,Georg Thieme Verlag, Stuttgart, New York, 1998, on page 491 under theentry on “reactive diluents”.

[0180] Examples of suitable light stabilizers are HALS compounds,benzotriazoles or oxalanilides.

[0181] Examples of suitable antioxidants are hydrazines and phosphoruscompounds.

[0182] Examples of suitable polymerization inhibitors are organicphosphites or 2,6-di-tert-butylphenol derivatives.

[0183] Examples of suitable thermolabile free-radical initiators aredialkyl peroxides, hydroperoxides peresters, azo dinitriles orC—C-cleaving initiators.

[0184] Examples of suitable photoinitiators are described in RömppChemie Lexikon, 9th, expanded and revised edition, Georg Thieme Verlag,Stuttgart, Vol. 4, 1991, or in Römpp Lexikon Lacke und Druckfarben,Georg Thieme Verlag, Stuttgart, 1998, pages 444 to 446.

[0185] Examples of suitable crosslinking catalysts are bismuth lactate,citrate, ethylhexanoate or dimethylol-propionate, dibutyltin dilaurate,lithium decanoate or zinc octoate, amine-blocked organic sulfonic acids,quaternary ammonium compounds, amines, imidazole and imidazolederivatives such as 2-styrylimidazole, 1-benzyl-2-methylimidazole,2-methylimidazole and 2-butylimidazole, as described in the Belgianpatent no. 756,693, or phosphonium catalysts such asethyltriphenylphosphonium iodide, ethyltriphenylphosphonium chloride,ethyltriphenylphosphonium thiocyanate, ethyltriphenylphosphoniumacetate-acetic acid complex, tetrabutylphosphonium iodide,tetrabutylphosphonium bromide and tetrabutylphosphonium acetate-aceticacid complex, as described, for example, in the U.S. patents U.S. Pat.No. 3,477,990 A or U.S. Pat. No. 3,341,580 A.

[0186] Examples of suitable devolatilizers are diazadicyclo-undecane orbenzoin.

[0187] Examples of suitable wetting agents are siloxanes, fluorinecompounds, carboxylic monoesters, phosphates, polyacrylic acids andtheir copolymers, or polyurethanes.

[0188] An example of a suitable adhesion promoter istricyclodecanedimethanol.

[0189] Examples of suitable film-forming auxiliaries are cellulosederivatives.

[0190] An example of a suitable flatting agent is magnesium stearate.

[0191] Further examples of the additives listed above and also ofsuitable leveling agents, flame retardants, siccatives, dryers,antiskinning agents, corrosion inhibitors, biocides, and waxes aredescribed in detail in the textbook “Lackadditive” [Additives forcoatings] by Johan Bieleman, Wiley-VCH, Weinheim, New York, 1998.

[0192] Further suitable additives include low-boiling and high-boiling(“long”) organic solvents, as are commonly used in the field of coatingmaterials. In view of the fact that the powder slurries and powdercoating materials of the invention are preferably free of VOCs, theorganic solvents are used only in exceptional cases.

[0193] In the process of the invention it is preferred to useemulsifiers as well. Suitable emulsifiers of this kind are the customaryand known emulsifiers, such as are described, for example, in the patentapplications cited at the outset. Further examples of emulsifiers arenonionic emulsifiers, such as alkoxylated alkanols and polyols, phenolsand alkylphenols or anionic emulsifiers such as alkali metal salts orammonium salts of alkanecarboxylic acids, alkanesulfonic acids, andsulfo acids of alkoxylated alkanols and polyols, phenols andalkylphenols.

[0194] For the preparation of the powder coating materials of theinvention it is preferred to use an emulsifier whose aqueous solution atthe critical micelle concentration (CMC) has a surface tension >30,preferably >35, and in particular >40 mN/m.

[0195] In the context of the present invention, the critical micelleconcentration (CMC) is the characteristic concentration at which above acertain temperature (the Krafft point) micelles form from surfactantmolecules in aqueous solutions (cf. Römpp-Chemie-Lexikon, Georg ThiemeVerlag, Stuttgart, New York, 9th edition, 1991, volume 4, pages 2769 and2770, “micelles”).

[0196] Accordingly, emulsifiers suitable for preparing the powdercoating materials of the invention are all ionic and nonionicemulsifiers which meet this condition.

[0197] Particularly preferred emulsifiers used are copolymers preparableby single-stage or multistage, especially single-stage, free-radical,especially controlled free-radical, copolymerization of

[0198] (a) at least one olefinically unsaturated monomer and

[0199] (b) at least one olefinically unsaturated monomer different thanthe olefinically unsaturated monomer (a) and of the general formula I

R¹R²C═CR³R⁴  (I),

[0200]  in which the radicals R¹, R², R³ and R⁴ each independently ofone another are hydrogen atoms or substituted or unsubstituted alkyl,cycloalkyl, alkylcycloalkyl, cycloalkylalkyl, aryl, alkylaryl,cycloalkylaryl, arylalkyl or arylcycloalkyl radicals, with the provisothat at least two of the variables R¹, R², R³ and R⁴ are substituted orunsubstituted aryl, arylalkyl or arylcycloalkyl radicals, especiallysubstituted or unsubstituted aryl radicals;

[0201] in an aqueous medium.

[0202] Examples of suitable monomers (a) are

[0203] (a1) substantially acid-group-free (meth)acrylic esters such as(meth)acrylic alkyl or cycloalkyl esters having up to 20 carbon atoms inthe alkyl radical, especially methyl, ethyl, propyl, n-butyl, sec-butyl,tert-butyl, hexyl, ethylhexyl, stearyl and lauryl acrylate ormethacrylate; cycloaliphatic (meth)acrylic esters, especiallycyclohexyl, isobornyl, dicyclopentadienyl,octahydro-4,7-methano-1H-indenemethanol acrylate or tert-butylcyclohexyl(meth)acrylate; (meth)acrylic oxaalkyl esters or oxacycloalkyl esterssuch as ethyltriglycol (meth)acrylate and methoxyoligoglycol(meth)acrylate having a molecular weight Mn of preferably 550, or otherethoxylated and/or propoxylated hydroxyl-free (meth)acrylic acidderivatives. These may contain minor amounts of (meth)acrylic alkyl orcycloalkyl esters of higher functionality, such as the di(meth)acrylatesof ethylene glycol, propylene glycol, diethylene glycol, dipropyleneglycol, butylene glycol, 1,5-pentanediol, 1,6-hexanediol,octahydro-4,7-methano-1H-indenedimethanol or 1,2-, 1,3- or1,4-cyclohexanediol; trimethylolpropane di- or tri(meth)acrylate; orpentaerythritol di-, tri- or tetra(meth)acrylate. For the purposes ofthe present invention, minor amounts of monomers of higher functionalityin this case are to be understood as amounts which do not lead tocrosslinking or gelling of the copolymers.

[0204] (a2) Monomers which carry per molecule at least one hydroxylgroup, amino group, alkoxymethylamino group or imino group and aresubstantially free from acid groups, such as hydroxyalkyl esters ofacrylic acid, methacrylic acid or another alpha,beta-olefinicallyunsaturated carboxylic acid, which derive from an alkylene glycolesterified with the acid, or which are obtainable by reacting thealpha,beta-olefinically unsaturated carboxylic acid with an alkyleneoxide, especially hydroxyalkyl esters of acrylic acid, methacrylic acid,ethacrylic acid, crotonic acid, maleic acid, fumaric acid or itaconicacid in which the hydroxyalkyl group contains up to 20 carbon atoms,such as 2-hydroxyethyl, 2-hydroxypropyl, 3-hydroxypropyl,3-hydroxybutyl, 4-hydroxybutyl acrylate, methacrylate, ethacrylate,crotonate, maleate, fumarate or itaconate; or hydroxycycloalkyl esterssuch as 1,4-bis(hydroxymethyl)cyclohexane,octahydro-4,7-methano-1H-indenedimethanol or methylpropanediolmonoacrylate, monomethacrylate, monoethacrylate, monocrotonate,monomaleate, monofumarate or monoitaconate; or reaction products ofcyclic esters, such as epsilon-caprolactone, for example, and thesehydroxyalkyl or hydroxycycloalkyl esters; or olefinically unsaturatedalcohols such as allyl alcohol or polyols such as trimethylolpropanemonoallyl or diallyl ether or pentaerythritol monoallyl, diallyl ortriallyl ether (as far as these monomers (a2) of higher functionalityare concerned, the comments made above relating to the monomers (a1) ofhigher functionality apply analogously); N,N-dimethylaminoethylacrylate, N,N-diethylaminoethyl methacrylate, allylamine orN-methyliminoethyl acrylate or N,N-di(methoxymethyl)aminoethyl acrylateand methacrylate or N,N-di(butoxymethyl)aminopropyl acrylate andmethacrylate.

[0205] (a3) Monomers which carry per molecule at least one acid groupwhich can be converted to the corresponding acid anion group, such asacrylic acid, methacrylic acid, beta-carboxyethyl acrylate, ethacrylicacid, crotonic acid, maleic acid, fumaric acid or itaconic acid;olefinically unsaturated sulfonic or phosphonic acids or their partialesters; or mono(meth)acryloyloxyethyl maleate, succinate or phthalate.

[0206] (a4) Vinyl esters of alpha-branched monocarboxylic acids having 5to 18 carbon atoms in the molecule. The branched monocarboxylic acidscan be obtained by reacting formic acid or carbon monoxide and waterwith olefins in the presence of a liquid, strongly acidic catalyst; theolefins may be cracking products of paraffinic hydrocarbons, such asmineral oil fractions, and may comprise both branched and straight-chainacyclic and/or cycloaliphatic olefins. The reaction of such olefins withformic acid or, respectively, with carbon monoxide and water produces amixture of carboxylic acids in which the carboxyl groups are locatedpredominantly on a quaternary carbon atom.

[0207] Examples of other olefinic starting materials are propylenetrimer, propylene tetramer and diisobutylene. Alternatively, the vinylesters (a4) may be prepared in a conventional manner from the acids, byreacting, for example, the acid with acetylene. Particular preference,owing to their ready availability, is given to using vinyl esters ofsaturated aliphatic monocarboxylic acids having 9 to 11 carbon atomsthat are branched on the alpha carbon atom, but especially Versatic®acids.

[0208] (a5) Reaction products of acrylic acid and/or alpha-branchedmonocarboxylic acid having 5 to 18 carbon atoms per molecule, especiallya Versatic® acid, or, instead of the reaction product, an equivalentamount of acrylic acid and/or methacrylic acid which is then reactedduring or after the polymerization reaction with the glycidyl ester ofan alpha-branched monocarboxylic acid having 5 to 18 carbon atoms permolecule, especially a Versatic® acid.

[0209] (a6) Cyclic and/or acyclic olefins such as ethylene, propylene,1-butene, 1-pentene, 1-hexene, cyclohexene, cyclopentene, norbornene,butadiene, isoprene, cyclopentadiene and/or dicyclopentadiene.

[0210] (a7) (Meth)acrylamides such as (meth)acrylamide, N-methyl-,N,N-dimethyl-, N-ethyl-, N,N-diethyl-, N-propyl-, N,N-dipropyl-,N-butyl-, N,N-dibutyl-, N-cyclohexyl-, N,N-cyclohexylmethyl- and/orN-methylol-, N,N-dimethylol-, N-methoxymethyl-, N,N-di(methoxymethyl)-,N-ethoxymethyl- and/or N,N-di(ethoxymethyl)-(meth)acrylamide. Monomersof the last-mentioned kind are used in particular to prepareself-crosslinking binders (A).

[0211] (a8) Monomers containing epoxide groups, such as the glycidylester of acrylic acid, methacrylic acid, ethacrylic acid, crotonic acid,maleic acid, fumaric acid and/or itaconic acid.

[0212] (a9) Vinylaromatic hydrocarbons such as styrene,alpha-alkylstyrenes, especially alpha-methylstyrene, and/orvinyltoluene; vinylbenzoic acid (all isomers), N,N-diethylaminostyrene(all isomers), alpha-methylvinylbenzoic acid (all isomers),N,N-diethylamino-alpha-methylstyrene (all isomers) and/orp-vinylbenzenesulfonic acid.

[0213] (a10) Nitriles such as acrylonitrile and/or methacrylonitrile.

[0214] (a11) Vinyl compounds, especially vinyl halides and/or vinylidenedihalides such as vinyl chloride, vinyl fluoride, vinylidene dichlorideor vinylidene difluoride; N-vinylamides such as vinyl-N-methylformamide,N-vinylcaprolactam, 1-vinylimidazole or N-vinylpyrrolidone; vinyl etherssuch as ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether,n-butyl vinyl ether, isobutyl vinyl ether and/or vinyl cyclohexyl ether;and/or vinyl esters such as vinyl acetate, vinyl propionate, vinylbutyrate, vinyl pivalate and/or the vinyl ester of2-methyl-2-ethylheptanoic acid.

[0215] (a12) Allyl compounds, especially allyl ethers and allyl esterssuch as allyl methyl, ethyl, propyl or butyl ether or allyl acetate,propionate or butyrate.

[0216] (a13) Polysiloxane macromonomers having a number-averagemolecular weight Mn of from 1000 to 40,000 and having on average from0.5 to 2.5 olefinically unsaturated double bonds per molecule;especially polysiloxane macromonomers having a number-average molecularweight Mn of from 2000 to 20,000, with particular preference from 2500to 10,000 and, in particular, from 3000 to 7000 and having on averagefrom 0.5 to 2.5, preferably from 0.5 to 1.5, olefinically unsaturateddouble bonds per molecule, as are described in DE-A-38 07 571 on pages 5to 7, in DE-A-37 06 095 in columns 3 to 7, in EP-B-0 358 153 on pages 3to 6, in U.S. Pat. No. 4,754,014 in columns 5 to 9, in DE-A-44 21 823 orin the international patent application WO 92/22615 on page 12 line 18to page 18 line 10.

[0217] (a14) Acryloxysilane-containing vinyl monomers, preparable byreacting hydroxy-functional silanes with epichlorohydrin and thenreacting the reaction product with (meth)acrylic acid and/or withhydroxyalkyl and/or hydroxycycloalkyl esters of (meth)acrylic acid (cf.monomers a2).

[0218] Each of the abovementioned monomers (a1) to (a14) may bepolymerized on their own with the monomers (b). In accordance with theinvention, however, it is advantageous to use at least two monomers (a),in particular at least one monomer (a1) and at least one monomer (a3),since by this means it is possible to vary the profile of properties ofthe resulting copolymers very widely, in a particularly advantageousmanner, and to tailor said profile of properties to the particularprocess of the invention. In particular, it is possible in this way toincorporate into the copolymers functional groups by means of which thecopolymers may be incorporated by crosslinking into the coatings,adhesive films, and seals produced from the powder slurries and powdercoating materials of the invention.

[0219] Monomers (b) used comprise compounds of the general formula I.

[0220] In the general formula I, the radicals R¹, R², R³ and R⁴ eachindependently of one another are hydrogen atoms or substituted orunsubstituted alkyl, cycloalkyl, alkylcycloalkyl, cycloalkylalkyl, aryl,alkylaryl, cycloalkylaryl, arylalkyl or arylcycloalkyl radicals, withthe proviso that at least two of the variables R¹, R², R³ and R⁴ aresubstituted or unsubstituted aryl, arylalkyl or arylcycloalkyl radicals,especially substituted or unsubstituted aryl radicals.

[0221] Examples of suitable alkyl radicals are methyl, ethyl, propyl,isopropyl, n-butyl, isobutyl, tert-butyl, amyl, hexyl or 2-ethylhexyl.

[0222] Examples of suitable cycloalkyl radicals are cyclobutyl,cyclopentyl or cyclohexyl.

[0223] Examples of suitable alkylcycloalkyl radicals aremethylenecyclohexane, ethylenecyclohexane orpropane-1,3-diylcyclohexane.

[0224] Examples of suitable cycloalkylalkyl radicals are 2-, 3- or4-methyl-, -ethyl-, -propyl- or -butylcyclohex-1-yl.

[0225] Examples of suitable aryl radicals are phenyl, naphthyl orbiphenylyl.

[0226] Examples of suitable alkylaryl radicals are benzyl or ethylene-or propane-1,3-diylbenzene.

[0227] Examples of suitable cycloalkylaryl radicals are 2-, 3 or4-phenylcyclohex-1-yl.

[0228] Examples of suitable arylalkyl radicals are 2-, 3- or 4-methyl-,-ethyl-, -propyl- or -butylphen-1-yl.

[0229] Examples of suitable arylcycloalkyl radicals are 2-, 3 or4-cyclohexylphen-1-yl.

[0230] The above-described radicals R¹, R², R³ and R⁴ may besubstituted. The substituents used may comprise ejectron-withdrawing orelectron-donating atoms or organic radicals.

[0231] Examples of suitable substituents are halogen atoms, especiallychlorine and fluorine, nitrile groups, nitro groups, partially or fullyhalogenated, especially chlorinated and/or fluorinated, alkyl,cycloalkyl, alkylcycloalkyl, cycloalkylalkyl, aryl, alkylaryl,cycloalkylaryl, arylalkyl and arylcycloalkyl radicals, including thoseexemplified above, especially tert-butyl; aryloxy, alkyloxy andcycloalkyloxy radicals, especially phenoxy, naphthoxy, methoxy, ethoxy,propoxy, butyloxy or cyclohexyloxy; arylthio, alkylthio andcycloalkylthio radicals, especially phenylthio, naphthylthio,methylthio, ethylthio, propylthio, butylthio or cyclohexylthio; hydroxylgroups; and/or primary, secondary and/or tertiary amino groups,especially amino, N-methylamino, N-ethylamino, N-propylamino,N-phenylamino, N-cyclohexylamino, N,N-dimethylamino, N,N-diethylamino,N,N-dipropylamino, N,N-diphenylamino, N,N,-dicyclohexylamino,N-cyclohexyl-N-methylamino and N-ethyl-N-methylamino.

[0232] Examples of monomers (b) whose use is particularly preferred inaccordance with the invention are diphenylethylene,dinaphthaleneethylene, cis- or trans-stilbene,vinylidenebis(4-N,N-dimethylamino-benzene),vinylidenebis(4-aminobenzene), and vinylidenebis(4-nitrobenzene).

[0233] In accordance with the invention, the monomers (b) may be usedindividually or as a mixture of at least two monomers (b).

[0234] In terms of the reaction regime and the properties of theresultant copolymers, especially the acrylate copolymers,diphenylethylene is of very particular advantage and is therefore usedwith very particular preference in accordance with the invention.

[0235] The monomers (a) and (b) to be used in accordance with theinvention are reacted with one another in the presence of at least onefree-radical initiator to form the copolymer. Examples of initiatorswhich can be used are: dialkyl peroxides, such as di-tert-butyl peroxideor dicumyl peroxide; hydroperoxides, such as cumene hydroperoxide ortert-butyl hydroperoxide; peresters, such as tert-butyl perbenzoate,tert-butyl perpivalate, tert-butyl per-3,5,5-trimethylhexanoate ortert-butylper-2-ethylhexanoate; potassium, sodium or ammoniumperoxodisulfate; azodinitriles such as azobisisobutyronitrile;C-C-cleaving initiators such as benzpinacol silyl ethers; or acombination of a nonoxidizing initiator with hydrogen peroxide.

[0236] It is preferred to add comparatively large amounts offree-radical initiator, the proportion of the initiator in the reactionmixture being, based in each case on the overall amount of the monomers(a) and of the initiator, with particular preference from 0.5 to 50% byweight, with very particular preference from 1 to 20% by weight, and inparticular from 2 to 15% by weight.

[0237] Preferably, the weight ratio of initiator to the monomers (b) isfrom 4:1 to 1:4, with particular preference from 3:1 to 1:3, and inparticular from 2:1 to 1:2. Further advantages result if the initiatoris used in excess within the stated limits.

[0238] The free-radical copolymerization is preferably conducted in theapparatus mentioned above, especially stirred tanks or Taylor reactors,the Taylor reactors being designed such that the conditions of Taylorflow are met over the entire reactor length, even if the kinematicviscosity of the reaction medium alters greatly, and in particularincreases, owing to the copolymerization.

[0239] The copolymerization is conducted in an aqueous medium.

[0240] The aqueous medium substantially comprises, or consists of,water. The aqueous medium may include minor amounts of the additivesand/or organic solvents and/or other dissolved solid, liquid or gaseousorganic and/or inorganic substances of low and/or high molecular mass,described above in detail, provided these do not adversely affect, oreven inhibit, the copolymerization. In the context of the presentinvention, the term “minor amount” means an amount which does not removethe aqueous character of the aqueous medium.

[0241] The copolymerization is preferably conducted in the presence ofat least one base. Particular preference is given to low molecular massbases such as sodium hydroxide solution, potassium hydroxide solution,ammonia, diethanolamine, triethanolamine, mono-, di- and triethylamine,and/or dimethylethanolamine, especially ammonia and/or di- and/ortriethanolamine.

[0242] The copolymerization is advantageously conducted at temperaturesabove room temperature and below the lowest decomposition temperature ofthe monomers used in each case, preference being given to a chosentemperature range of from 10 to 150° C., with very particular preferencefrom 70 to 120° C., and in particular from 80 to 110° C.

[0243] When using particularly volatile monomers (a) and/or

[0244] (b), the copolymerization may also be conducted under pressure,preferably under from 1.5 to 3000 bar, with particular preference from 5to 1500 bar, and in particular from 10 to 1000 bar.

[0245] In terms of the molecular weight distributions, there are norestrictions whatsoever imposed on the copolymer. Advantageously,however, the copolymerization is conducted so as to give a molecularweight distribution Mw/Mn, measured by gel permeation chromatographyusing polystyrene as standard, of ≦4, with particular preference ≦2, andin particular ≦1.5, and in certain cases even ≦1.3. The molecularweights of the constituents (A) may be controlled within wide limits bythe choice of ratio of monomer (a) to monomer (b) to free-radicalinitiator. In this context, the amount of monomer (b) in particulardetermines the molecular weight, specifically such that the higher theproportion of monomer (b), the lower the resultant molecular weight.

[0246] The copolymer resulting from the copolymerization is obtained asa mixture with the aqueous medium, generally in the form of adispersion. In this form it can be used as an emulsifier directly orelse isolated as a solid and then passed on for use in accordance withthe invention.

[0247] The emulsifier may be introduced, in particular in the form of asolid, into the melts and/or, in particular in the form of a dispersion,into the aqueous media. Preferably it is introduced in the form of adispersion into the aqueous media.

[0248] In one particular preferred embodiment of the process of theinvention, employed first and foremost when preparing pigmented powdercoating materials of the invention, the particularly preferredemulsifier is introduced into the aqueous media via at least one of theabove-described pigment pastes or pigment preparations. Or else thepigment pastes or pigment preparations in question constitute theaqueous medium.

[0249] The amount of the emulsifiers that is used in the process of theinvention may vary greatly and is guided by the requirements of eachindividual case. For instance, they may be used in the customary amountsknown from the prior art for emulsifiers. They are preferably used in anamount of from 0.01 to 5.0, more preferably from 0.02 to 4.5, withparticular preference from 0.03 to 4, with very particular preferencefrom 0.04 to 3.5, and in particular from 0.05 to 3% by weight, based ineach case on the amount of the melted or solid particles and theemulsifiers.

[0250] The powder coating materials of the invention possess outstandingfluidity, storage properties, and transport properties, and exhibit nocaking even on prolonged storage. Their application characteristics areoutstanding. They are outstandingly suitable as, or for preparing,coating materials, adhesives, and sealing compounds.

[0251] The coating materials of the invention are outstandingly suitablefor producing single-coat or multicoat, color and/or effect,electrically conductive, magnetically shielding or fluorescent coatings,such as primer-surfacer coats, basecoats, solid-color topcoats orcombination effect coats, or single-coat or multicoat clearcoat systems.

[0252] The adhesives of the invention are outstandingly suitable forproducing adhesive films, and the sealing compounds of the invention areoutstandingly suitable for producing seals.

[0253] Very particular advantages result when the unpigmented powdercoating materials of the invention are used as clearcoat materials forproducing single-coat or multicoat clearcoat systems. In particular, theclearcoat materials of the invention are used to produce multicoat colorand/or effect coating systems by the wet-on-wet technique, in which abasecoat material, especially an aqueous basecoat material, is appliedto the surface of a substrate, and then the resultant basecoat film,without being cured, is dried and is overcoated with a clearcoat film.Thereafter the two films are cured together.

[0254] Very particularly advantages result when the pigmented powdercoating materials of the invention are used to produce single-coat ormulticoat color and/or effect coating systems or combination effectcoats. A combination effect coat is a coating which performs at leasttwo functions in a color and/or effect system. Functions of this kindinclude in particular protection against corrosion, adhesion promotion,the absorption of mechanical energy, and the imparting of color and/oreffect. Preferably, the combination effect coat serves to absorbmechanical energy and to impart color and/or effect at the same time; ittherefore fulfills the functions of a primer-surfacer coat orantistonechip primer and of a basecoat. Preferably, the combinationeffect coat additionally has a corrosion protection effect and/oradhesion promotion effect.

[0255] The pigmented coatings or coating systems may likewise beproduced using wet-on-wet techniques. For example, the pigmented powdercoating materials of the invention may be applied to electrocoat filmswhich have not been cured, or not been cured fully, and then the filmsone above the other are cured together.

[0256] The very particular advantage of the powder coating materials ofthe invention is that they can be used to produce all kinds of multicoatpaint systems based completely or predominantly on the powder coatingmaterials of the invention.

[0257] The application of the powder coating materials also has nospecial features in terms of its method but instead takes place, forexample, in accordance with the customary and known fluidized-bedtechniques, such as are known, for example, from the BASF Coatings AGbrochures “Pulverlacke, für industrielle Anwendungen” [Powder coatingmaterials for industrial applications], January 2000, or “CoatingsPartner, Pulverlack Spezial” [Powder coatings special], January 2000, orRömpp Lexikon Lacke und Druckfarben, Georg Thieme Verlag, Stuttgart, NewYork, 1998, pages 187 and 188, “electrostatic powder spraying”,“electrostatic spraying” and “electrostatic fluidized bath process”.

[0258] Suitable substrates are all those whose surface is not damaged bythe application of heat and/or actinic radiation in the course of thecuring of the films present thereon. Preferably, the substrates comprisemetals, plastics, wood, ceramic, stone, textile, fiber composites,leather, glass, glass fibers, glass wool and rockwool, mineral- andresin-bound building materials, such as plasterboard and cement slabs orroof tiles, and also composites of these materials.

[0259] Accordingly, the coating materials, adhesives, and sealingcompounds are outstandingly suitable for coating, bonding, and sealingmotor vehicle bodies, parts of motor vehicle bodies, the interior andexterior of motor vehicles, the inside and outside of buildings, doors,windows, furniture, and for coating, bonding and sealing in the contextof the industrial coating, for example, of small parts, such as nuts,bolts, wheel rims or hubcaps, coils, containers, packaging, electricalcomponents, such as motor windings or transformer windings, and of whitegoods, such as domestic appliances, boilers, and radiators.

[0260] In the case of electrically conductive substrates it is possibleto use primers produced conventionally from the electrodepositioncoating materials. Both anodic and cathodic electrocoat materials aresuitable for this purpose, but especially cathodic electrocoatmaterials. Unfunctionalized and/or nonpolar plastics surfaces may besubjected prior to coating in a known manner to a pretreatment, such aswith a plasma or by flaming, or may be provided with a water-basedprimer.

[0261] The curing of the applied powder coating materials of theinvention also has no special features in terms of its method but itthen takes place in accordance with the customary and known thermalmethods, such as heating in a forced air oven or irradiation using IRlamps. For actinic radiation curing, suitable radiation sources includethose such as high- or low-pressure mercury vapor lamps, which may bedoped with lead in order to open up a radiation window up to 405 nm, orelectron beam sources. Examples of suitable techniques and apparatus forcuring with actinic radiation are described in the German patentapplication DE 198 18 735 A1, column 10 lines 31 to 61.

[0262] The resultant coatings of the invention, especially thesingle-coat or multicoat color and effect coating systems, combinationeffect coats and clearcoat systems of the invention are easy to produceand have outstanding optical properties and very high light, chemical,water, condensation, and weathering resistance. In particular they arefree from turbidities and inhomogeneities. They are hard, flexible, andscratch resistant. They have very good reflow properties and outstandingintercoat adhesion, and exhibit good to very good adhesion to customaryand known automotive refinishes.

[0263] The adhesive films of the invention bond a very wide variety ofsubstrates to one another firmly and durably and possess high chemicaland mechanical stability even in the case of extreme temperatures and/ortemperature fluctuations.

[0264] Similarly, the seals of the invention seal the substrates durablyand possess high chemical and mechanical stability even in the case ofextreme temperatures and/or temperature fluctuations and even inconjunction with exposure to aggressive chemicals.

[0265] A further advantage of the dual-cure coating materials,adhesives, and sealing compounds is that, even in the shadow zones ofthree-dimensional substrates of complex shape, such as vehicle bodies,radiators or electrical wound goods, and even without optimum—especiallycomplete—elimination of the shadow zones with actinic radiation, theyproduce coatings, adhesive films, and seals whose profile of performanceproperties is at least equal to that of the coatings, adhesive films,and seals outside the shadow zones. As a result, the coatings, adhesivefilms and seals in the shadow zones are also no longer readily damagedby mechanical and/or chemical attack, as may occur, for example, whenfurther components of motor vehicles are installed in the coated bodies.

[0266] Accordingly, the primed or unprimed substrates which are commonlyemployed in the technological fields set out above and which are coatedwith at least one coating of the invention, bonded with at least oneadhesive film of the invention and/or sealed with at least one seal ofthe invention combine a particularly advantageous profile of performanceproperties with a particularly long service life, so making themparticularly attractive economically.

EXAMPLES Preparation Example 1

[0267] The Preparation of an Emulsifier

[0268] A suitable reaction vessel fitted with three feed vessels,stirrer, reflux condenser, and oil heating, was charged with 52.56 partsby weight of deionized water and this initial charge was heated to 90°Celsius. Thereafter, at this temperature, three separate feed streamswere metered in to the initial charge in parallel and at a uniform rate.The first feed stream consisted of 10.18 parts by weight of acrylicacid, 18.35 parts by weight of methyl methacrylate, and 1.49 parts byweight of diphenyl ethylene. The second feed stream consisted of 9.9parts by weight of a 25% strength by weight ammonia solution in water.The third feed stream consisted of a solution of 2.25 parts by weight ofammonium peroxodisulfate in 5.25 parts by weight of deionized water. Thefirst and second feed streams were metered in over the course of onehour. The third feed stream was metered in over the course of 1.25hours. After the end of the addition, polymerization was continued forfour hours. During this time the temperature of the reaction mixture wasslowly reduced. The result was a dispersion of the emulsifier having asolids content of 33% by weight. The aqueous solution of the emulsifierhad a surface tension of 50 mN/m at the critical micelle concentration.

Preparation Example 2

[0269] The Preparation of a Binder

[0270] The binder was prepared by solution polymerization of 25 parts byweight of styrene, 36 parts by weight of methyl methacrylate, 28 partsby weight of glycidyl methacrylate and 11 parts by weight of butylmethacrylate in xylene at 140° Celsius. As initiator, 6.7 parts byweight of tert-butyl perethylhexanoate were used. Followingpolymerization, the solvent was stripped. The resulting solid resin hada number-average molecular weight of 4 200 Daltons and an epoxideequivalent weight of 550 g/mol. It was heated to process temperature ina melt vessel.

Example 1

[0271] The Preparation of a Powder Coating Material of the Invention

[0272] Three heatable melt containers were connected via metering pumpsto a static Sulzer mixer (empty volume: 0.0463 liter). The exit of themixer was connected to a toothed-ring dispersing unit (K-Generator fromKinematica AG, Lucerne, Switzerland) into which a continuous aqueousphase was metered in parallel to the disperse phase (the mixture of thethree melts).

[0273] The first melt container contained a mixture of

[0274] 95.1% by weight of the melted resin of Preparation Example 2,

[0275] 2.5% by weight of Tinuvin® CGL 1545 (commercial UV absorber fromCiba Specialty Chemicals),

[0276] 1.3% by weight of Tinuvin® 123 (commercial reversiblefree-radical scavenger, HALS, from Ciba Specialty Chemicals),

[0277] 0.3% by weight of Irgafos® P-EPQ (commercial antioxidant fromCiba Specialty Chemicals),

[0278] 0.8% by weight Troy® EX 542 (commercial benzoin-containingdevolatilizer from Troy, USA).

[0279] The melt was pumped into the mixer at a process temperature of152° C. and a mass flow rate of 34 kg/h. Its disperse phase fraction was73.6% by weight.

[0280] The second melt container contained dodecanedioic acid, which ata process temperature of 154° C. was pumped into the mixer at a massflow rate of 7.2 kg/h. Its disperse phase fraction was 16.2% by weight.

[0281] The third melt container contained a 3,5-dimethylpyrazole-blockedpolyisocyanate based on isophorone diisocyanate, having an NCO contentof 15.5% by weight, which at a process temperature of 134° C. was pumpedinto the mixer at a mass flow rate of 5.0 kg/h. Its disperse phasefraction was 10.8% by weight.

[0282] After a residence time of 3.5 s, the melt entered the chamber ofthe toothed-ring dispersing unit.

[0283] From a further feed vessel the continuous aqueous phasecomprising 95% by weight deionized water and 5.0% by weight emulsifierdispersion from Preparation Example 1 was metered at a mass flow rate of77.5 kg/h in parallel to the metering of the melts.

[0284] The rotary speed of the toothed-ring dispersing unit was 9000rpm.

[0285] After leaving the toothed-ring dispersing unit the resultingemulsion cooled rapidly using a pipe cooler. The resulting suspensionhad a z-average particle size of 12.9 μm (measured using the Malvernlaser diffraction instrument) and a solids content of 37.5% by weight(one hour/130° Celsius).

[0286] The suspension was fully sedimentation-stable and had outstandingtransport and application properties. Moreover, it was outstandinglysuitable for the preparation of powder coating materials.

[0287] The suspension was sprayed in a spraying tower such that thetemperature of the particles did not rise above 40° C. The temperatureof the stream of drying air was 110° C. The water content of the powdercoating material of the invention was below 0.5% by weight. Its averageparticle size was 25 μm.

[0288] The powder coating material of the invention was stable instorage and in transit and showed no tendency to cake. Its fluidity andits application properties were outstanding. It gave smooth, highlyglossy, scratch-resistant, flexible, hard, and chemical-resistantclearcoats having outstanding adhesion properties.

What is claimed is:
 1. A powder coating material preparable by (1)mixing at least two liquid components comprising in each case at leastone liquid starting product in a static mixer, to give a molecularlydisperse and/or finely dispersed liquid mixture, (2) emulsifying theliquid mixture (1) in an aqueous medium in a dispersing unit, to give anaqueous emulsion of liquid particles, (3) cooling the emulsion (2) sothat a suspension of dimensionally stable particles is formed, and (4)isolating the dimensionally stable particles from the suspension (3) oralternatively (3) isolating the dimensionally stable particles directlyfrom the emulsion (2).
 2. The powder coating material as claimed inclaim 1, wherein at least one of the liquid components is a melt.
 3. Thepowder coating material as claimed in claim 1 or 2, wherein at least oneof the liquid components comprises or consists of a binder melt.
 4. Thepowder coating material as claimed in any of claims 1 to 3, wherein atleast one of the melts comprises or consists of a crosslinking agentmelt.
 5. The powder coating material as claimed in any of claims 1 to 4,wherein at least one of the liquid components comprises liquid or solidadditives.
 6. The powder coating material as claimed in any of claims 1to 5, wherein the residence time of the melts in the static mixer isfrom 0.5 to 20 seconds.
 7. The powder coating material as claimed in anyof claims 1 to 6, wherein an inline dissolver is used as dispersingunit.
 8. The powder coating material as claimed in claim 7, wherein theinline dissolver is a toothed-ring dispersing unit comprising at leastone cylindrical arrangement of at least two comminutor rings (stator androtor) which are seated on holders, are in mutual embrace, and arerotatable in opposite directions relative to one another, the workinggap produced by the relative movement between stator and rotor havingwalls which extend nonparallelwise with respect to one another.
 9. Thepowder coating material as claimed in any of claims 1 to 8, wherein theresidence time of the liquid mixture (1) and of the aqueous medium inthe dispersing unit is from 0.5 to 20 seconds.
 10. The powder coatingmaterial as claimed in any of claims 1 to 9, wherein the dimensionallystable particles are isolated from the suspensions (3) by spray dryingor freeze drying.
 11. The powder coating material as claimed in any ofclaims 1 to 10, wherein the dimensionally stable particles are isolatedfrom the emulsions (2) by pressure relief.
 12. The powder coatingmaterial as claimed in any of claims 1 to 11, wherein at least of theliquid components and/or the aqueous medium comprise at least oneemulsifier.
 13. The powder coating material as claimed in claim 12,wherein the aqueous solution of the emulsifier at the critical micelleconcentration (CMC) has a surface tension >30 mN/m.
 14. The powdercoating material as claimed in claim 12 or 13, wherein the emulsifier isselected from the group of copolymers preparable by single-stage ormultistage free-radical copolymerization in an aqueous medium of (a) atleast one olefinically unsaturated monomer and (b) at least oneolefinically unsaturated monomer different than the olefinicallyunsaturated monomer (a) and of the general formula I R¹R²C═CR³R⁴  (I) in which the radicals R¹, R², R³, and R⁴ each independently of oneanother are hydrogen atoms or substituted or unsubstituted alkyl,cycloalkyl, alkylcycloalkyl, cycloalkylalkyl, aryl, alkylaryl,cycloalkylaryl, arylalkyl or arylcycloalkyl radicals with the provisothat at least two of the variables R¹, R², R³ and R⁴ are substituted orunsubstituted aryl, arylalkyl or arylcycloalkyl radicals, especiallysubstituted or unsubstituted aryl radicals.
 15. The powder coatingmaterial as claimed in claim 14, wherein the aryl radicals R¹, R², R³and/or R⁴ of the monomers (b) are phenyl or naphthyl radicals.
 16. Thepowder coating material as claimed in claim 14, wherein the radicals arephenyl radicals.
 17. The powder coating material as claimed in any ofclaims 14 to 16, wherein the substituents in the radicals R¹, R², R³ andR⁴ of the monomers (b) are selected from the group consisting ofelectron-withdrawing or electron-donating atoms or organic radicals. 18.The powder coating material as claimed in claim 17, wherein thesubstituents are selected from the group consisting of halogen atoms,nitrile, nitro, partially or fully halogenated alkyl, cycloalkyl,alkylcycloalkyl, cycloalkylalkyl, aryl, alkylaryl, cycloalkylaryl,arylalkyl, and arylcycloalkyl radicals; aryloxy, alkyloxy, andcycloalkyloxy radicals; arylthio, alkylthio, and cycloalkylthioradicals, and primary, secondary and/or tertiary amino groups.
 19. Thepowder coating material as claimed in any of claims 14 to 18, wherein atleast one monomer (a) is selected from the group of thecarboxyl-containing monomers (a3).
 20. The powder coating material asclaimed in any of claims 12 to 19, wherein the emulsifier is present inthe aqueous medium.
 21. The powder coating material as claimed in any ofclaims 1 to 20, curable physically or thermally and/or with actinicradiation.
 22. The powder coating material as claimed in any of claims 1to 21, which is a one-component system.
 23. The powder coating materialas claimed in any of claims 12 to 22, which is pigmented.
 24. A processfor preparing a pigmented powder coating material as claimed in any ofclaims 1 to 23, which comprises (1) mixing at least two liquidcomponents comprising in each case at least one liquid starting productin a static mixer, to give a molecularly disperse and/or finelydispersed liquid mixture, (2) emulsifying the liquid mixture (1) in anaqueous medium in a dispersing unit, to give an aqueous emulsion ofliquid particles, (3) cooling the emulsion (2) so that a suspension ofdimensionally stable particles is formed, and (4) isolating thedimensionally stable particles (3) from the suspension, or alternatively(3) isolating the dimensionally stable particles directly from theemulsion (2).
 25. The process as claimed in claim 24, wherein theaqueous medium in step (2) consists in whole or in part of an aqueouspigment preparation (pigment paste).
 26. The use of a powder coatingmaterial as claimed in any of claims 1 to 23 as a coating material,adhesive or sealing compound or to prepare a coating material, adhesive,or sealing compound.
 27. The use as claimed in claim 26, wherein thecoating material, adhesive or sealing compound is curable physically orthermally and/or with actinic radiation.
 28. The use as claimed in claim27, wherein the coating material, adhesive or sealing compound is usedto coat, bond, and seal motor vehicle bodies and parts thereof, theinterior and exterior of motor vehicles, doors, windows, furniture, andalso for coating, bonding, and sealing as part of the industrial coatingof small parts, coils, containers, packaging, electrical components, andwhite goods.